You have formulated a hypothesis: “Apples contain more vitamin C than oranges.”
To test your hypothesis you measure vitamin C levels in 20 oranges and 20 apples from trees that were grown in the same orchard under the same environmental conditions (temperature, rain, sunlight). This experiment was conducted twice. The control in the experiment is ?__________________________________.
a) type of soil, temperature, amount of rain and sunlight in the orchard
b) vitamin C levels
e) a large sample size and repeated experiment